Improving drought resilience, yield stability, and grain carbohydrate compositions of guar through integrated nutrient and water management approaches

Drought stress is one of the major constraints limiting crop productivity, particularly in arid and semi-arid regions. This study evaluated the effects of integrated water and nutrient management, including deficit irrigation, superabsorbent polymer, and fertilizer management, on physiological responses, antioxidant defense, nutrient acquisition, grain quality, yield-related attributes, and irrigation water-use efficiency of guar ( Cyamopsis tetragonoloba L.) under field conditions. The experiment was conducted during two consecutive growing seasons (2023–2024 and 2024–2025) in Kerman Province, Iran, using a split-factorial arrangement based on a randomized complete block design with three replications. Irrigation regimes (100, 75, and 50% field capacity), SAP application, and five fertilizer management strategies significantly affected most evaluated traits. Water deficit reduced plant height, relative water content, membrane stability, photosynthetic pigments, nutrient uptake, grain protein, galactomannan components, and yield, while increasing oxidative damage and osmotic adjustment responses. Application of SAP improved plant water status, photosynthetic pigment accumulation, grain quality, yield, and irrigation water-use efficiency, mainly through enhanced water availability and nutrient uptake. Integrated fertilizer management, particularly FM2 (100% chemical fertilizer) and FM3 (75% chemical fertilizer combined with microbial consortium), effectively mitigated drought-induced limitations by improving antioxidant capacity, mineral nutrition, and yield attributes. The highest grain yield (2253.30 kg ha ^− 1 ) and irrigation water-use efficiency (0.38 kg m ^− 3 ) were obtained under 100% FC × FM3, which were comparable to those under 100% FC × FM2. In contrast, severe drought without fertilization resulted in the lowest productivity. Overall, the integration of SAP and sustainable nutrient management strategies, especially microbial-based fertilizer management, enhanced drought resilience and productivity of guar, suggesting their potential application for sustainable production of this drought-tolerant legume in water-limited environments.